How can you tell who’s real on Facebook?

Am I just being dumb here or is it pure guess work who's really who on Facebook? I'm new to Facebook as I've had privacy concerns though finding out about "Limited User" has eased those a little.

As far as I can see it's trivial for me to set myself up as any celebrity I choose as there isn't any kind of "registration authority" to bind physical and logical identities - if the was one who would we all trust? Clearly obtaining the photograph of a celebrity is trivial.

Personally i’d hope though (un)common sense that Joe Public would atleast look on said celebrities official site for mention of “Hey look at my MySpace/Live Space/Facebook/Bebo/Hi5” ad infinitum, as opposed to blindly handing “open” access to they’re own details. Thesad trut of the matter is until we go “Nanny State”, or people become not only aware of security but practise good conduct, the world and it’s interweb are dangerous places.